Composite has been widely used as a light weight and high strength structure material due to advantages such as high specific strength and specific rigidity. In certain applications such as some specific parts in a propeller plane, some functional composite laminates is also needed as covering protective layers. On one hand, such composite can absorb sound, reduce vibration and lower noise; on the other hand, the composite can also have good shock resistance for example. to be used in a plane body which can endure accidental strikes by debris. Therefore, the composite can not only have functionalities such as sound absorption, vibration reduction, thermal insulation and noise cancellation, but also can serve as a weak load bearing structure. Other typical applications for such composite include inner decoration for the airplanes, ground transportations and ships. Foam material is one kind of composite with low density and moderate and adjustable mechanical property. Depending on the material selection and structure design, foam material can also have functionalities such as vibration reduction and noise cancellation, low thermal conduction and thermal insulation, as well as serving as filler. Therefore, it can be used within a cabin or used as inner decoration in vehicles, trains, airplanes and household. However, foam materials have a common trait of relative low rigidity and strength.
The mechanical properties of the above foam material can be significantly improved by fibers, particularly long fibers or continuous fibers. To this end, some trinary composite foam laminates are proposed. A fabricating method of a web like composite foam made by a trinary material of fibers, curable thermosetting resin and expandable micro spheres was disclosed by U.S. Pat. No. 4,483,889 entitled “Method for the production of fiber composite materials impregnated with resin” disclosed. An expandable microsphere with thermal foaming agent encapsulated by expandable polymer was disclosed by U.S. Pat. No. 4,513,106 entitled “Process for expandable microspheres”. An expandable microsphere with thermal foaming agent encapsulated by expandable polymer shell was disclosed by U.S. Pat. No. 5,834,526 entitled “Expandable hollow particles”. The above patented technologies can be used to fabricate a continuous glass fiber reinforced composite foam laminate, which is now commercially available.
However, the above continuous fibers used in the above technologies are conventional solid fiber materials, such as glass fiber, carbon fiber or organic synthetic fiber, which do not have good functionalities in vibration reduction and noise cancellation as well as sound absorption and insulation. Therefore they can not be used in applications specifically demanding for vibration reduction and low noise, such as inner walls and floor of engine chamber.
Plant fibers come from natural crops which are conventionally used to manufacture papers, clothes or ropes etc. . . . The hollow structure in some plant fibers enables excellent properties of sound absorption, vibration reduction, heat insulation, noise cancellation and damping. They also have good specific strength and specific rigidity and relatively low cost, therefore those plant fibers can be applied in the composite as environmentally friendly material.
However, plant fibers and resin matrix in the composite have poor interface compatibility, which adversely affects mechanical properties of the composite. In addition, plant fibers are too flammable to be used in fireproof-demanded applications.
In Chinese patent application No. 200610150159.7 entitled “Plant fiber glass steel composite and fabricating method thereof”, Chinese patent application No. 200410028501.7 entitled “Thermal pressing fabricating method of polyethylene fiber-plant fiber composite” and Chinese patent application No. 200610062751.1 entitled “Plant fiber composite laminate and producing process thereof”, plant fibers in forms of powders or short fibers are used to fill in or reinforce the composite, and plant plane fibers are not subjected to a preliminary treatment. Therefore the composite has poor interface compatibility and consequently has low mechanical properties.
Fiber-metal laminate is new hybrid-reinforced composite abbreviated generally as FML laminate. The typical examples of FML include aramid-aluminum laminate abbreviated as ARALL and glass-reinforced aluminum abbreviated as GLARE. A method of fabricating such composite laminate was described in detail in US patents (U.S. Pat. Nos. 5,039,571, 5,547,735 and 5,219,629) and a non-patent literature (Vogelesang, L., Development of a New Hybrid Material (ARALL) for Aircraft Structure, Ind. Eng. Chem. Prod. Res. Dev., 1983, pp. 492-496). Currently, GLARE has been widely applied to the upper body of A380 plane body.